代码

package com.xcrj;

/** * 剑指 Offer II 021. 删除链表的倒数第 n 个结点 * 给定一个链表,删除链表的倒数第 n 个结点,并且返回链表的头结点. */
public class Solution21 {
    

    /** * The two pointers move in the same direction,iPoints to the current node of the traversal,j指向从i倒数第n个结点,当i-j=n时,j移动,最终当i指向最后1个元素是,j指向倒数第n个元素 * Insert before the head node1个结点（伪头结点）,It is not necessary to consider how to deal with the head node separately */
    public ListNode removeNthFromEnd3(ListNode head, int n) {
    
        // Construct a pseudo-header node,Inserted before the head of the linked list1个新的结点,The penultimate may not be processed separatelynA node is the head node
        ListNode dummy = new ListNode(0, head);
        ListNode pi = head;
        ListNode pj = dummy;
        // pi先走n步
        for (int i = 0; i < n; ++i) {
    
            pi = pi.next;
        }
        // pi和pj同时往后走,直到pireach the end point,此时pj就是倒数第n个结点
        while (pi != null) {
    
            pi = pi.next;
            pj = pj.next;
        }
        pj.next = pj.next.next;
        // The next node of the pseudo-head node is the head node
        return dummy.next;
    }

    public static void main(String[] args) {
    

    }
}

参考

作者：LeetCode-Solution
链接：https://leetcode.cn/problems/SLwz0R/solution/shan-chu-lian-biao-de-dao-shu-di-n-ge-ji-ydte/
来源：力扣（LeetCode）